The present invention relates to a single action cylinder for use with a machine which machine has a first part and a second part having reciprocating motion relative to each other for affecting the reciprocation between said first and second parts.
It is well known to use pneumatic cushions and counterbalances having stacked resilient actuators with a wide variety of machines, such as, power presses, welders, and the like. The benefits which are derived from the utilization of stacked actuators in a cushion or counterbalance are appreciated, however, there is a problem in the utilization of stacked actuators. It may be appreciated that the cushion or counterbalance typically contains some sort of guide for the stacked actuators which requires that the direction of movement of the cushion or counterbalance must be parallel to the direction of movement of a movable portion of a machine such as a press or a welder. Furthermore, it may be appreciated that the guides or ways for a machine may not be perfectly straight and the guide of the cushion or counterbalance may not be perfectly straight either. If the divergence from the required norm of both the guide or way of the machine and the guide of the counterbalance or cushion are too great or in opposite directions, there may be a binding of the reciprocating parts of the machine or of the cushion or counterbalance. The binding typically results from extraneous loadings on the relatively reciprocating parts of the machine as well as the relatively reciprocating parts of the cushion or counterbalance. The extraneous loading not only causes a loss of power, but also abnormal wear on the parts of the machine and the cushions or counterbalance which reduces the life expectancy of all of the parts.
The utilization of cushions having guide rods in a power press is disclosed in detail in U.S. Letters Patent No. 4,732,033, issued Mar. 22, 1988, to Smedberg et al, and entitled, "Pneumatic Die Cushion". A specific disclosure of a counterbalance used in conjunction with a press is disclosed in U.S. Letters Patent No. 4,736,615, issued April 12, 1988, to Smedberg et al, and entitled, "Pneumatic Press Counterbalance". Another cushion construction for use with a press is taught in U.S. Letters Patent No. 4,796,460, issued Jan. 10, 1989, to Smedberg et al, and entitled, "Cushion Construction Including Snubber". It may be seen from all of the disclosures how the guides for the counterbalance or die cushions are substantially rigid in relation to the movement of reciprocating parts of a press so that non-alignment of the die cushion or the counterbalance results in extraneous loadings on the reciprocating parts.
Stacking of the resilient actuators is well known and accepted in the transportation industry. U.S. Pat. Ser. No. 2,773,686, issued Dec. 11, 1956, to C.B. Nash, entitled "Air Spring" discloses a construction wherein two bellows are interconnected. The Nash connector utilizes a conventional construction. The conventional construction for bellows of this type is also shown in the following patents: U.S. Pat. Ser. No. 2,827,283, issued Mar. 18, 1958, to K.A. Browne et al., entitled, "Air Spring With Damping Valve"; U.S. Pat. Ser. No 2,887,069, issued May 19, 1959, to R.L. Rich, entitled, "Air Spring Railway Truck"; U.S. Pat. Ser. No. 2,902,291, issued Sept. 1, 1959, to L.B. Walker, entitled, "Vehicle Pneumatic Suspension System"; and U.S. Pat. Ser. No. 2,999,682, issued Sept. 12, 1961, to E. Stump, entitled, "Pneumatic Spring System For Motor Vehicles".
It is an object of the present invention to provide an improved single action cylinder having stacked actuators which cylinder substantially eliminates binding of parts having reciprocating motion relative to each other when the single action cylinder is used in conjunction with the parts even though there is imperfect alignment between the cylinder and the parts.